Scanner induced pattern shifts between layers are a large contributor to DRAM Bitline to Active overlay. One of the main root causes for this Pattern Shift non-Uniformity are lens aberrations. Currently measuring the Bitline to Active overlay requires a decap CDSEM method1. In this paper, an in-resist pattern shift uniformity metrology method is proposed which quantifies the main DRAM Bitline to Active overlay without the necessity to decap. We have designed a high transmission reticle (≥ 60%) to measure the pattern shift non-uniformity between two dense gratings under the rotation angle of the Active layer in both cold and hot lens states. Each module on the reticle contains product-like features and a variety of metrology targets, i.e. alignment and overlay, such that the product-to-product and the productto- metrology pattern shift fingerprints can be measured. OPC is applied to enlarge the overlapping process windows of the metrology targets with respect to the product-like features.
As device structures continue to shrink and new materials are introduced, Three Dimensional (3D) Metrology becomes
more important. The creation of 3D Metrology data is defined as the generation of statistically relevant 3D information
used in R&D and/or semiconductor manufacturing. Parameters of interest are: profile shape, side wall angle, material
properties, height of the structure, as well as the variation within a die, on the wafer, between wafers. In this paper we
will show how this information is used to calibrate process control systems in a semiconductor fab. Also, results will be
shown on how this information may be used to compare different types of Metrology equipment e.g. CD-SEM and
optical CD metrology techniques like scatterometry.
Certain applications, such as the generation of profile information for 55 nm dense contact holes in photoresist, require
new technology to minimize damage to the soft photoresist. A new technique called in-situ broadband argon cleaning
will be presented. Finally, the application of the argon column for protective coating deposition of sub-45 nm photoresist
lines will be discussed.
The International Technology Roadmap for Semiconductors (ITRS) provides a set of Metrology specifications as targets
for each technology node. In the current edition (2007) of the ITRS the conventional precision (reproducibility) is
replaced with a new metric - measurement uncertainty for dimensional metrology. This measurement uncertainty
contains single tool precision, tool-to-tool matching, sampling uncertainty, and inaccuracy (sample-to-sample bias
variation and other effects). Clearly, sampling uncertainty is a major component of measurement uncertainty. This paper
elaborates on sampling uncertainty and provides statistical estimates for sampling uncertainty. The authors in this paper
address the importance and the methods of proper sampling. The correct sampling captures and allows for the expression
of the information needed for adequate patterning process control. Along with typical manufacturing process control
cases (excursion control, advanced and statistical process control), several other applications are explored such as optical
and electron beam line width measurement calibration, measurement tool evaluations, lithographic scanner assessment
and optical proximity correction implementation. The authors show how appropriate choices among measurement
techniques, sampling methods, and interpretation of measurement results give meaningful information for process
control and demonstrate how an incorrect choice can lead to wrong conclusions.
Proc. SPIE. 6152, Metrology, Inspection, and Process Control for Microlithography XX
KEYWORDS: Cadmium, Etching, Electron microscopes, Atomic force microscopy, Scanning electron microscopy, Line width roughness, Critical dimension metrology, Line edge roughness, Scanning transmission electron microscopy, Edge roughness
This study demonstrates the MPPC (Multiple Parameters Profile Characterization) measurement method utilizing ArF photo resist patterns. MPPC is a technique for estimating the three dimensional profile of patterns which are imaged and measured on the CD-SEM (critical dimension scanning electron microscope). MPPC utilizes the secondary electron signal to calculate several indices including top CD, peak CD, top rounding, bottom footing, etc.
This primary focused of this study is to understand the variations in pattern profile caused by changes in exposure condition. The results demonstrate the ability to extract pattern profile shape information by MPPC measurement that could not otherwise be detected by a conventional bottom CD measurement method. Furthermore, the results were compared to cross sectional images collected by STEM (scanning transmission electron microscope) to verify the accuracy of the MPPC technique. The peak CD results accurately estimate the pattern width when the sidewall angle of the feature is nearly vertical. Additionally, line edge roughness (LER) caused by pattern profile variations was evaluated utilizing MPPC. The results suggest that MPPC may be utilized to evaluate the roughness over the entire profile.
This paper presents a novel method of FIB (FIB: focused ion beam) sample preparation to accurately evaluate critical dimensions and profiles of ArF photo resist patterns without the use of a protective coating on the photo resist. In order to accomplish this, the FIB micro-sampling method that is one of effective FIB milling and fabrication method was employed. First a Si cap is picked up from a silicon wafer and fixed to ArF photo resist patterns to protect against ion beam irradiation. Then, a micro-sample, a piece of Si-capped ArF photo resist, was extracted from the bulk ArF photo resist. In this procedure, this silicon cap always protects ArF photo resist patterns against ion beam irradiation. For the next step, the micro-sample is fixed to a needle stub of the FIB-STEM (STEM: scanning transmission electron microscopy) compatible rotation holder. This sample on the needle stub was rotated 180 degrees and milled from the side of Si substrate. Lastly, the sample is milled to the thickness of 2μm. In this process, the ion beam is irradiating from the silicon substrate side to minimize the ion beam irradiation damages on the ArF photo resist patterns. EDX (EDX: Energy dispersive X-ray spectroscopy) analysis proved that no gallium ions were detected on the surface of the ArF photo resist patterns. The feasibility of high accelerating voltage observation of STEM to observe line edge roughness of a thick sample like 2μm without shrinkage has been demonstrated.